Wednesday, March 5, 2008

Drosophila is a genus of small flies, belonging to the familyDrosophilidae, whose members are often called "fruit flies" or more appropriately vinegar flies, wine flies, pomace flies, grape flies, and picked fruit-flies, a reference to the characteristic of many species to linger around overripe or rotting fruit. A second, related fly family, the Tephritidae, are also called fruit flies; these feed primarily on unripe or ripe fruit, with many species being regarded as destructive agricultural pests, especially the Mediterranean fruit fly. One species of Drosophila in particular, D. melanogaster, has been heavily used in research in genetics and is a common model organism in developmental biology. Indeed, the terms "fruit fly" and "Drosophila" are often used synonymously with D. melanogaster in modern biological literature. The entire genus, however, contains about 1,500 species and is very diverse in appearance, behavior, and breeding habitat. Scientists who do research on Drosophila are often called Drosophilists. NameDrosophila are small flies, typically pale yellow to reddish brown to black, with red eyes. Many species, including the noted Hawaiian picture-wings, have distinct black patterns on the wings. The plumose (feathery) arista, bristling of the head and thorax, and wing venation are characters used to diagnose the family. Most are small, about 2–4 millimetres long, but some, especially many of the Hawaiian species, are larger than a house fly. Morphology Life cycle and ecologyDrosophila are found all around the world, with more species in the tropical regions. They can be found in deserts, tropical rainforest, cities, swamps, and alpine zones. Some northern species hibernate. Most species breed in various kinds of decaying plant and fungal material, including fruit, bark, slime fluxes, flowers, and mushrooms. A few species have switched to being parasites or predators. Many species can be attracted to baits of fermented bananas or mushrooms, but others are not attracted to any kind of baits. Males may congregate at patches of suitable breeding substrate to compete for the females, or form leks, conducting courtship in an area separate from breeding sites. Several Drosophila species, including D. melanogaster, D. immigrans, and D. simulans, are closely associated with humans, and are often referred to as domestic species. These and other species (D. subobscura, Zaprionus indianus) have been accidentally introduced around the world by human activities such as fruit transports. Habitat Males of this genus are known to have the longest sperm cells of any organism on Earth, including one species, Drosophila bifurca, that have sperm that are 5.8 centimetres long. D. melanogaster sperm cells are a more modest 1.8 millimetres long, although this is still about 300 times as long as a human sperm.Drosophila vary widely in their reproductive capacity. Those such as D. melanogaster that breed in large, relatively rare resources have ovaries that mature 10–20 eggs at a time, so that they can be laid together on one site. Others that breed in more-abundant but less nutritious substrates, such as leaves, may only lay one egg per day. The eggs have one or more respiratory filaments near the anterior end; the tips of these extend above the surface and allow oxygen to reach the embryo. Larvae feed not on the vegetable matter itself but on the yeasts and microorganisms present on the decaying breeding substrate. Development time varies widely between species (between 7 and more than 60 days) and depends on the environmental factors such as temperature, breeding substrate, and crowding. Laboratory–cultured animalsDrosophila are prey for many generalist predators such as robber flies. In Hawaii, the introduction of yellowjackets from the mainland United States has led to the decline of many of the large species. The larvae are preyed on by other fly larvae, staphylinidbeetles, and ants. SystematicsDrosophila are extensively used as a model organism in genetics (including population genetics), cell-biology, biochemistry, and especially developmental biology. Therefore, extensive efforts are made to sequence drosphilid genomes. The genomes of the following species have been fully or partially sequenced so far: The data will be used for many purposes, including evolutionary genome comparisons. D. simulans and D. sechellia are sister species, and provide viable offspring when crossed, while D. melanogaster and D. simulans produce infertile hybrid offspring. The Drosophila genome is often compared with the genomes of more distantly related species such as the honeybeeApis mellifera or the mosquitoAnopheles gambiae. Curated data are available at FlyBase.Drosophila (Sophophora) melanogaster[1]Drosophila (Sophophora) simulans[2]Drosophila (Sophophora) sechellia[3]Drosophila (Sophophora) yakuba[4]Drosophila (Sophophora) erecta[5]Drosophila (Sophophora) ananassae[6]Drosophila (Sophophora) pseudoobscura[7]Drosophila (Sophophora) persimilis[8]Drosophila (Sophophora) willistoni[9]Drosophila (Drosophila) mojavensis[10]Drosophila (Drosophila) virilis[11]Drosophila (Drosophila) grimshawi[12]